osl_unmapFile can't work for files bundled inside the .apk on Android

On Android, when an app is installed, arbitrary files bundled in the
app won't be unpacked into actual separate files in the file
system. They will exist only as archive entries in the .apk file
(which is a zip archive).

The SDK tooling puts such files under the /assets folder in the
.apk. The LibreOffice bootstrapping code for Android maps the .apk
file into memory.

osl_openFile() knows about the /assets special case, and uses a
separate abstraction for such memory-mapped files.

Obviously, when producing an .apk, one needs to make sure these
bundled files are not compressed, if one wants to be able to use them
directly from the memory-mapped .apk file. We do that in our test and
sample Android projects.

When mapping such files under /assets , just return a pointer to the
file's location inside the mapped .apk archive.

We can't use the old osl_unmapFile() on such mapped files, as that
would unexpectedly unmap fairly arbitrary pages of the .apk mapping,
wreaking havoc on later use of the same pages.

So, introduce a new osl_unmapMappedFile() function that takes also the
oslFileHandle originally passed to osl_mapFile(). Use this instead in
the few places where the code actually called osl_unmapFile(). Make
sure osl_mapFile() is nonexistent on Android.

6 files changed, 112 insertions, 19 deletions

diff --git a/sal/inc/osl/file.h b/sal/inc/osl/file.h
index cc12b1c616f8..ecf9e60a4d68 100644
--- a/sal/inc/osl/file.h
+++ b/sal/inc/osl/file.h
@@ -680,6 +680,12 @@ typedef void *oslFileHandle;
     @param uFlags [in]
     Specifies the open mode.
 
+    On Android, if the file path is below the /assets folder, the file
+    exists only as a hopefully uncompressed element inside the app
+    package (.apk), which has been mapped into memory as a whole by
+    the LibreOffice Android bootstrapping code. So files "opened" from
+    there aren't actually files in the OS sense.
+
     @return
     osl_File_E_None on success<br>
     osl_File_E_NOMEM not enough memory for allocating structures <br>
@@ -837,6 +843,15 @@ SAL_DLLPUBLIC oslFileError SAL_CALL osl_getFileSize(
 
 /** Map a shared file into memory.
 
+    Don't know what the "shared" is supposed to mean there? Also,
+    obviously this API can be used to map *part* of a file into
+    memory, and different parts can be mapped separately even.
+
+    On Android, if the Handle refers to a file that is actually inside
+    the app package (.apk zip archive), no new mapping is created,
+    just a pointer to the file inside the already mapped .apk is
+    returned.
+
     @since UDK 3.2.10
  */
 SAL_DLLPUBLIC oslFileError SAL_CALL osl_mapFile (
@@ -848,8 +863,19 @@ SAL_DLLPUBLIC oslFileError SAL_CALL osl_mapFile (
 );
 
 
+#ifndef ANDROID
+
 /** Unmap a shared file from memory.
 
+    Ditto here, why do we need to mention "shared"?
+
+    This function just won't work on Android in general where for
+    (uncompressed) files inside the .apk, per SDK conventions in the
+    /assets folder, osl_mapFile() returns a pointer to the file inside
+    the already by LibreOffice Android-specific bootstrapping code
+    mmapped .apk archive. We can't go and randomly munmap part of the
+    .apk archive. So this function is not present on Android.
+
     @since UDK 3.2.10
  */
 SAL_DLLPUBLIC oslFileError SAL_CALL osl_unmapFile (
@@ -857,6 +883,25 @@ SAL_DLLPUBLIC oslFileError SAL_CALL osl_unmapFile (
   sal_uInt64 uLength
 );
 
+#endif
+
+/** Unmap a file segment from memory.
+
+    Like osl_unmapFile(), but takes also the oslFileHandle argument
+    passed to osl_mapFile() when creating this mapping.
+
+    On Android, for files below /assets, i.e. located inside the app
+    archive (.apk), this won't actually unmap anything; all the .apk
+    stays mapped.
+
+    @since UDK 3.6
+ */
+SAL_DLLPUBLIC oslFileError SAL_CALL osl_unmapMappedFile (
+  oslFileHandle Handle,
+  void*      pAddr,
+  sal_uInt64 uLength
+);
+
 
 /** Read a number of bytes from a file.
 
diff --git a/sal/osl/unx/file.cxx b/sal/osl/unx/file.cxx
index f0604131e34a..458554ea9e4f 100644
--- a/sal/osl/unx/file.cxx
+++ b/sal/osl/unx/file.cxx
@@ -865,7 +865,6 @@ SAL_CALL osl_openMemoryAsFile( void *address, size_t size, oslFileHandle *pHandl
         eRet = oslTranslateFileError (OSL_FET_ERROR, ENOMEM);
         return eRet;
     }
-    pImpl->m_kind = FileHandle_Impl::KIND_MEM;
     pImpl->m_size = sal::static_int_cast< sal_uInt64 >(size);
 
     *pHandle = (oslFileHandle)(pImpl);
@@ -1116,13 +1115,7 @@ SAL_CALL osl_mapFile (
 {
     FileHandle_Impl* pImpl = static_cast<FileHandle_Impl*>(Handle);
 
-    if (pImpl->m_kind == FileHandle_Impl::KIND_MEM)
-    {
-        *ppAddr = pImpl->m_buffer;
-        return osl_File_E_None;
-    }
-
-    if ((0 == pImpl) || (-1 == pImpl->m_fd) || (0 == ppAddr))
+    if ((0 == pImpl) || ((pImpl->m_kind == FileHandle_Impl::KIND_FD) && (-1 == pImpl->m_fd)) || (0 == ppAddr))
         return osl_File_E_INVAL;
     *ppAddr = 0;
 
@@ -1134,6 +1127,13 @@ SAL_CALL osl_mapFile (
     static sal_uInt64 const g_limit_off_t = std::numeric_limits< off_t >::max();
     if (g_limit_off_t < uOffset)
         return osl_File_E_OVERFLOW;
+
+    if (pImpl->m_kind == FileHandle_Impl::KIND_MEM)
+    {
+        *ppAddr = pImpl->m_buffer + uOffset;
+        return osl_File_E_None;
+    }
+
     off_t const nOffset = sal::static_int_cast< off_t >(uOffset);
 
     void* p = mmap(NULL, nLength, PROT_READ, MAP_SHARED, pImpl->m_fd, nOffset);
@@ -1195,11 +1195,9 @@ SAL_CALL osl_mapFile (
     return osl_File_E_None;
 }
 
-/*******************************************
-    osl_unmapFile
-********************************************/
+static
 oslFileError
-SAL_CALL osl_unmapFile (void* pAddr, sal_uInt64 uLength)
+unmapFile (void* pAddr, sal_uInt64 uLength)
 {
     if (0 == pAddr)
         return osl_File_E_INVAL;
@@ -1215,6 +1213,40 @@ SAL_CALL osl_unmapFile (void* pAddr, sal_uInt64 uLength)
     return osl_File_E_None;
 }
 
+#ifndef ANDROID
+
+// Note that osl_unmapFile() just won't work on Android in general
+// where for (uncompressed) files inside the .apk, in the /assets
+// folder osl_mapFile just returns a pointer to the file inside the
+// already mmapped .apk archive.
+
+/*******************************************
+    osl_unmapFile
+********************************************/
+oslFileError
+SAL_CALL osl_unmapFile (void* pAddr, sal_uInt64 uLength)
+{
+    return unmapFile (pAddr, uLength);
+}
+
+#endif
+
+/*******************************************
+    osl_unmapMappedFile
+********************************************/
+oslFileError
+SAL_CALL osl_unmapMappedFile (oslFileHandle Handle, void* pAddr, sal_uInt64 uLength)
+{
+    FileHandle_Impl * pImpl = static_cast<FileHandle_Impl*>(Handle);
+
+    if (pImpl->m_kind == FileHandle_Impl::KIND_FD)
+        return unmapFile (pAddr, uLength);
+
+    // For parts of already mmapped "parent" files, whose mapping we
+    // can't change, not much we can or should do...
+    return osl_File_E_None;
+}
+
 /*******************************************
     osl_readLine
 ********************************************/
diff --git a/sal/osl/w32/file.cxx b/sal/osl/w32/file.cxx
index da49f3a75b2c..5e73dbf62f3a 100644
--- a/sal/osl/w32/file.cxx
+++ b/sal/osl/w32/file.cxx
@@ -882,6 +882,13 @@ SAL_CALL osl_unmapFile(void* pAddr, sal_uInt64 /* uLength */)
 
 //#############################################
 oslFileError
+SAL_CALL osl_unmapMappedFile(oslFileHandle /* Handle */, void* pAddr, sal_uInt64 uLength)
+{
+    return osl_unmapFile( pAddr, uLength );
+}
+
+//#############################################
+oslFileError
 SAL_CALL osl_readLine(
     oslFileHandle   Handle,
     sal_Sequence ** ppSequence)
diff --git a/sal/util/sal.map b/sal/util/sal.map
index 7ccc24ca631b..e8a9ab520477 100644
--- a/sal/util/sal.map
+++ b/sal/util/sal.map
@@ -610,6 +610,11 @@ LIBO_UDK_3.5 { # symbols available in >= LibO 3.5
         rtl_uStringbuffer_remove;
 } UDK_3.10;
 
+LIBO_UDK_3.6 { # symbols available in >= LibO 3.6
+    global:
+        osl_unmapMappedFile;
+} UDK_3.10;
+
 PRIVATE_1.0 {
     global:
         osl_detail_ObjectRegistry_storeAddresses;
diff --git a/store/source/lockbyte.cxx b/store/source/lockbyte.cxx
index f7b20f002f7b..a91e470cc38d 100644
--- a/store/source/lockbyte.cxx
+++ b/store/source/lockbyte.cxx
@@ -476,6 +476,7 @@ struct FileMapping
 {
     sal_uInt8 * m_pAddr;
     sal_uInt32  m_nSize;
+    oslFileHandle m_hFile;
 
     FileMapping() : m_pAddr(0), m_nSize(0) {}
 
@@ -497,15 +498,17 @@ struct FileMapping
             return osl_File_E_OVERFLOW;
         m_nSize = sal::static_int_cast<sal_uInt32>(uSize);
 
+        m_hFile = hFile;
+
         // Acquire mapping.
         return osl_mapFile (hFile, reinterpret_cast<void**>(&m_pAddr), m_nSize, 0, osl_File_MapFlag_RandomAccess);
     }
 
     /** @see MappedLockBytes::destructor.
      */
-    static void unmapFile (sal_uInt8 * pAddr, sal_uInt32 nSize)
+    static void unmapFile (oslFileHandle hFile, sal_uInt8 * pAddr, sal_uInt32 nSize)
     {
-        (void) osl_unmapFile (pAddr, nSize);
+        (void) osl_unmapMappedFile (hFile, pAddr, nSize);
     }
 
     /** @see ResourceHolder<T>::destructor_type
@@ -515,7 +518,7 @@ struct FileMapping
         void operator ()(FileMapping & rMapping) const
         {
             // Release mapping.
-            unmapFile (rMapping.m_pAddr, rMapping.m_nSize);
+            unmapFile (rMapping.m_hFile, rMapping.m_pAddr, rMapping.m_nSize);
             rMapping.m_pAddr = 0, rMapping.m_nSize = 0;
         }
     };
@@ -532,6 +535,7 @@ class MappedLockBytes :
     sal_uInt8 * m_pData;
     sal_uInt32  m_nSize;
     sal_uInt16  m_nPageSize;
+    oslFileHandle m_hFile;
 
     /** PageData::Allocator implementation.
      */
@@ -577,13 +581,13 @@ protected:
 } // namespace store
 
 MappedLockBytes::MappedLockBytes (FileMapping & rMapping)
-    : m_pData (rMapping.m_pAddr), m_nSize (rMapping.m_nSize), m_nPageSize(0)
+    : m_pData (rMapping.m_pAddr), m_nSize (rMapping.m_nSize), m_nPageSize(0), m_hFile (rMapping.m_hFile)
 {
 }
 
 MappedLockBytes::~MappedLockBytes()
 {
-    FileMapping::unmapFile (m_pData, m_nSize);
+    FileMapping::unmapFile (m_hFile, m_pData, m_nSize);
 }
 
 oslInterlockedCount SAL_CALL MappedLockBytes::acquire()
diff --git a/xmlreader/source/xmlreader.cxx b/xmlreader/source/xmlreader.cxx
index 0801c8137474..05782eeb70dd 100644
--- a/xmlreader/source/xmlreader.cxx
+++ b/xmlreader/source/xmlreader.cxx
@@ -115,11 +115,11 @@ XmlReader::XmlReader(rtl::OUString const & fileUrl)
 }
 
 XmlReader::~XmlReader() {
-    oslFileError e = osl_unmapFile(fileAddress_, fileSize_);
+    oslFileError e = osl_unmapMappedFile(fileHandle_, fileAddress_, fileSize_);
     if (e != osl_File_E_None) {
         SAL_WARN(
             "xmlreader",
-            "osl_unmapFile of \"" << fileUrl_ << "\" failed with " << +e);
+            "osl_unmapMappedFile of \"" << fileUrl_ << "\" failed with " << +e);
     }
     e = osl_closeFile(fileHandle_);
     if (e != osl_File_E_None) {